Yes, we know. She's just a random woman sitting in front of our protagonist who happens to be eating peanuts. But her presence is actually invaluable for teaching us several key facts about our protagonist. Fact: the protagonist has not eaten all day, which points to the fact that he's poor. Fact: if the protagonist was in the South, he'd feel very comfortable asking her for some peanuts. He's is now in the North. For a woman who does nothing but sit in a seat and eat roasted peanuts, she sure plays a big role from a technical aspect of the writing.